The invention relates generally to an activatable power cell and applications for activatable power cells, including applications for such cells in electrocardiographic monitoring and transdermal drug delivery. In one particular embodiment, the invention relates to patient monitoring devices powered by an activated power cell and having a wireless connection between a patient and a remote location.
Biomedical electrodes have long been used for diagnostic and therapeutic purposes including electrocardiographic monitoring and diagnosis, electrosurgery, iontophoretic (electrically enhanced) transdermal delivery of drugs, and defibrillation. In their most basic form these electrodes have a conductive medium contacting mammalian skin and a means for electrical communication that interacts between the conductive medium and electrical diagnostic, therapeutic, or electrosurgical equipment. A cable connecting the electrode to the equipment is the most commonly used means to accomplish the electrical communication. The cable may be hardwired to the electrode or may releasably attach to it with, for example, a head-and-socket connection or a clasp and tab connection. While inexpensive, a cable restricts the mobility of the patient and risks the disconnection of the electrode from the equipment if the cable is inadvertently pulled.
As a way to overcome these disadvantages, remote (or wireless) monitoring systems have been suggested. These systems typically include a disposable self-contained, wireless electrode-transmitter unit that is applied to the patient and an adapter for receiving a transmitted signal from the transmitter unit and feeding it to a display device. Other enhancements such as digital transmission, error correction methodologies and reverse communication to the electrode (e.g., via a transceiver) have also been suggested to enhance the utility of wireless connection in the field the medical diagnostics. In spite of active research in this area, however, such systems have not been widely made commercially available. One reason inhibiting the practical utility of these systems is the unavailability of a suitable energy supply for the electrode.
Most small electronic devices, including wireless electrodes and drug delivery devices, require an energy source to perform calculations, process data, communicate with remote receivers and transmitters, and store information in an electronic memory system. A self-contained electronic device can theoretically be supplied with power either passively or actively. Passively, a device can receive energy radiated toward it from a remote source energy and accumulate it, using for example an inductor and a capacitor. There are, however, limits to the power that can be transmitted in this way and the range over which it can be transmitted, especially in a controlled environment such as a health care facility where problems of electromagnetic interference are particularly acute. An active energy source is normally supplied by a battery. While numerous types of batteries are available and commonly sold for use in watches, hearing aids and other electronic devices, such batteries typically are expensive, have limited shelf life and require special disposal considerations. For disposable electronic devices, such as biomedical electrodes and transdermal drug delivery devices, the expense of a battery in each electrode or device is difficult to justify and long term shelf stability is an important consideration where the products can be stored indefinitely in, for example, a first aid or other pre-assembled kit.
It is desirable, therefore, to provide a low cost, shelf stable power source for small electronic devices, including, in the medical field, biomedical electrodes and drug delivery devices.
The present invention provides a power source that comprises a galvanic cell in a partial state of construction. More specifically, in one aspect, the invention provides a galvanic cell that is activatable on demand. The cell comprises an anode conductor, a cathode conductor and an electrolyte-containing substance, where the electrolyte-containing substance is separated from at least one of the anode conductor or cathode conductor by an electrically insulative separator material until the cell is activated by removing the separator and allowing the electrolyte-containing substance to contact both the anode and cathode conductors.
In another aspect, the invention provides a biomedical electrode capable of communicating information between a patient and a remote location and having within it a galvanic cell in a state of partial construction. The biomedical electrode generally comprises:
(a) a first quantity of electrically conductive medium in electrical contact with a signal processing circuit adapted to communicate information to the remote location; and
(b) a galvanic cell connected to the signal processing circuit, the galvanic cell comprising an anode conductor, a cathode conductor, and electrolyte-containing substance, where the electrolyte-containing substance is separated from at least one of the anode conductor and the cathode conductor until the biomedical electrode is used on the patient.
In yet another aspect, the invention provides a method for obtaining and communicating electrical signals of electrophysiological or electrobiological origin from a patient, the method comprising:
providing a biomedical electrode comprising a first quantity of conductive medium in electrical contact with a signal processing circuit and a galvanic cell connected to signal processing circuit, the galvanic cell comprising an anode construction, a cathode construction, and electrolyte containing substance, where the electrolyte containing substance is separated from at least one of the anode and cathode constructions;
providing a second quantity of conductive medium in electrical contact with the signal processing circuit;
causing the electrolyte containing substance to contact the anode and cathode constructions;
applying the first quantity of conductive medium and the second quantity of conductive medium to the patient;
transducing electrical signals from the patient""s body to obtain diagnostic or therapeutic information; and
transmitting the information via the signal processing circuit.
In still another aspect, the invention emphasizes the utility of the galvanic cell as substantially described above for therapeutic devices. In this respect, the invention provides a device for delivering a pharmaceutically active agent, the device comprising:
a first quantity of electrically conductive medium and a second quantity of electrically conductive medium;
a galvanic cell comprising an anode conductor, a cathode conductor, and electrolyte-containing substance, where the anode conductor is in electrical contact with the first quantity of electrically conductive medium and the cathode conductor is in electrical contact with the second quantity of electrically conductive medium, and where the electrolyte-containing substance is separated from at least one of the anode and cathode conductors until the device is to be used on a patient; and
at least one quantity of pharmaceutically active agent capable of existing in an ionized state incorporated within one or both of the first quantity of electrically conductive medium or the second quantity of electrically conductive medium.
In yet another embodiment, the invention provides a device for delivering a pharmaceutically active agent, where the device comprises a galvanic cell that includes an anode conductor, a cathode conductor, and two fields of electrolyte-containing substance where prior to activation at least one field of electrolyte-containing substance is separated from at least one of the anode and cathode conductors and following activation the anode conductor is in electrical contact with one field of electrolyte-containing substance and the cathode conductor is electrical contact the second field of electrolyte-containing substance. At least one quantity of pharmaceutically active agent capable of existing in an ionized state is incorporated within at least one of the fields of electrolyte-containing substance.